1. Field of the Invention
The present invention relates to an electronic circuit unit in which electronic components or the like are built in a circuit substrate which is obtained by cutting an integral substrate to be separated, and a method of manufacturing the electronic circuit unit.
2. Description of the Related Art
After a plurality of circuit portions corresponding to a plurality of electronic circuit units is collectively provided on an integral substrate, a manufacturing method of cutting the integral substrate to be separated is a manufacturing method through which productivity can be improved significantly by a small electronic circuit unit having a circuit configuration of a high density. Due to this, when such an electronic circuit unit is manufactured, a wiring pattern, solder resist, and the like are collectively formed at each of a plurality of rectangular areas divided by vertical cut lines on the integral substrate, and electronic components or the like are collectively built in. After that, a method by which the integral substrate is cut along the cut lines with a dicing saw and thereby the electronic circuit unit is obtained in plural, is generally used. Meanwhile, in the electronic circuit unit manufactured in such a way, a portion corresponding to the rectangular area of the integral substrate is a circuit substrate.
As such an electronic circuit unit, an invention described in Japanese Unexamined Patent Application Publication No. 2011-018699 is disclosed. An electronic circuit unit 900 described in Japanese Unexamined Patent Application Publication No. 2011-018699 is illustrated in FIG. 6.
In the electronic circuit unit 900, a copper foil land 905 is provided at a corner portion of a circuit substrate 902 for the electronic circuit unit 900, and a corner space area 902b with an approximately L shape is extended between the substrate outer edge 902d which is at a right angle and divides the corner portions, and an outer peripheral edge expanding out of the copper foil land 905. Solder resist 906 is provided at only a relatively wide area in the immediate vicinity of the corner edge 902a in the corner space area 902b, and a narrow area distant from the corner edge 902a becomes a substrate exposure area 902c without the solder resist 906. The circuit substrate 902 is obtained by cutting the integral substrate 910 along a vertical cut line 911 and a horizontal cut line 912 so as to be separated, and a leg of a shield cover which covers a high frequency circuit portion on the circuit substrate 902 is inserted into an attachment hole 905a of the copper foil land 905 and is soldered.
In this way, in the electronic circuit unit 900, the solder resist 906 is provided at only a relatively wide area in the immediate vicinity of the corner edge 902a in the corner space area 902b of the circuit substrate 902. Then, if the narrow area distant from the corner edge 902a becomes the substrate exposure area 902c without the solder resist 906, when the integral substrate 910 is obtained by cutting along a vertical cut line 911 and a horizontal cut line 912 to be separated, it is difficult to peel the solder resist 906 in which a contact area with a substrate surface is sufficiently secured at the corner space area. Together with this, there is no concern that resin burr of substrate materials occurs in the vicinity of the corner edge 902a. In addition, although the resin burr occurs at the substrate exposure area 902c of both end portions of the corner space area due to a cutting process, the resin burr is not seen because the substrate exposure area 902c is distant from the corner edge 902a, and thus there is little possibility that appearance of the commercialized electronic circuit unit 900 is damaged.
However, since a length of the substrate exposure area 902c of the integral substrate 910 is relatively long, it was impossible to completely remove the resin burr in the electronic circuit unit 900. In addition, furthermore, when cutting the integral substrate 910, resist burr was found. When manufacturing the electronic circuit unit 900, flux cored reflow solder is used, but when soldering the leg of the shield cover, the flux spreads and remains solidified at the portion of the cut line. As a result, the resist remains interposed in the flux, and relatively long resist burr occurs. Thus, the resist burr is seen, and there is a problem that the appearance of the commercialized electronic circuit unit 900 is damaged.